Alzheimer’s, Blood Flow and Air Pollution

Scientists at the Montreal Neurological Institute and Hospital analyzed more than 7,700 brain images from 1,171 people in various stages of Alzheimer’s progression using a variety of techniques including magnetic resonance imaging (MRI) and positron emission tomography (PET). Blood and cerebrospinal fluid were also analyzed, as well as the subjects’ level of cognition. The researchers found that, contrary to previous understanding, the first physiological sign of Alzheimer’s disease is a decrease in blood flow in the brain. An increase in amyloid protein was considered to be the first detectable sign of Alzheimer’s. While amyloid certainly plays a role, this study finds that changes in blood flow are the earliest known warning sign of Alzheimer’s. The study also found that changes in cognition begin earlier in the progression than previously believed.

The Montreal Neurological Institute and Hospital – The Neuro – is a world-leading destination for brain research and advanced patient care. The Neuro has grown to be the largest specialized neuroscience research and clinical center in Canada, and one of the largest in the world. This study is one of the most thorough ever published on the subject of Alzheimer’s disease progression. The study used multiple imaging techniques to measure amyloid concentration, glucose metabolism, cerebral blood flow, functional activity and brain atrophy in 78 regions of the brain, covering all grey matter.

Late-onset Alzheimer’s disease is an incredibly complex disease that is not caused by any one neurological mechanism but is a result of several associated mechanisms in the brain. Late-onset Alzheimer’s disease is the most common cause of human dementia and an understanding of the interactions between its various mechanisms is important to develop treatments.

Emerging evidence suggests that there is a link between air pollution and dementia. Last month researchers at the University of Toronto published a study in The Lancet that found that dementia is more common in people who live within 50 meters of a major road than those who live further away. The researchers tracked all adults between the ages of 20 and 85 living in Ontario, Canada- approximately 6.6 million people - from 2001 to 2012. They used the Canadian postcodes to determine how close people lived to a road and analyzed medical records to see if they went on to develop dementia or other diseases. They found that over the study period, more than 243000 people developed dementia and those living within 50 meters of a major rad were 12% more likely to develop dementia. The researchers believe that fine particulate pollutants which are often 10 times higher near major roads are the cause.

Though the link between air pollution as fine particulates and dementia remains controversial, a growing number of epidemiological and animal studies are beginning to support that link. The association of inhaling fine particulates and heart disease has become well established, now with mounting evidence of accelerating cognitive aging and even increased risk of Alzheimer’s disease more research is needed to develop a deeper understanding of functioning of the brain. Possibly, inhaled particulates impair blood flow to the brain.  If you want to take a look at real time particulate pollution levels you can see what the monitors nearest your home are reporting. 

Alzheimer's disease is a progressive loss of memory and cognition, for which there is no cure. In Alzheimer’s disease aggregates of beta-amyloid form plaques between brain cells that is believed to contribute to the disease process, but in one of the earliest studies, the Nuns Study, beta-amyloid plaques were present when there were no signs of cognitive decline. Funding for research for treatment for Alzheimer’s disease gave a primary role for amyloid-in Alzheimer's disease, but treatment strategies targeted at reducing amyloid-have failed to reverse cognitive symptoms. These clinical findings suggest that cognitive decline is the result of a complex pathophysiology and that targeting amyloid-alone may not be sufficient to treat Alzheimer's disease. It also suggests that there will be no cure.